The present invention relates to lighting control systems and in particular to a lighting control method and apparatus to reduce power consumption of lighting systems.
As can be understood, there are numerous reasons to reduce power consumption of a lighting or other electrical system. The benefits include reduced power costs to the user and benefits to the environment. While it may be desirable to reduce an electrical system""s power consumption, it is preferred to not reduce or hinder operation of the electrical system. By way of example, a lighting system""s power consumption may be reduced by dimming the lights, but this may undesirably reduce the light output of the lighting system. The lighting system was likely installed and designed for a predetermined amount of input power or voltage and hence reducing the amount of the voltage defeats the purpose of the lighting systems.
It is known however that certain types of electrical systems may be provided less power without hindering operation. In the case of lighting systems, it is known in the prior art that high intensity discharge (HID) and flourescent lighting systems may be operated at a lower voltage after operation for a short time at full power. Power savings through dimming may be realized without appreciable amount of reduced light output. For example, the change in light output can not be detected by the human eye.
In systems of the prior art a transformer is utilized to modify the voltage. As is understood, a transformer is capable of modifying a signal""s voltage level. Through a reduction in voltage supplied to the lights, power saving may be realized. In systems of the prior art, one or more transformers are utilized to step up the voltage to a level suitable for driving the high power HID or flourescent lighting systems. After a short period of time, the transformer operation may be modified or the signal directed to an additional transformer to step-down the voltage. Stepping down the voltage through one or more additional transformer devices reduces the voltage to thereby allow a savings in power consumption.
While it is desirable to reduce power consumption in lighting or other electrical systems by reducing the voltage supplied to these systems reliable and dependable, operation must be maintained. In one example installation, HID and flourescent lighting may be installed in a parking lot, parking garage, or building interior. If the power saving systems malfunctions, the lights may be rendered inoperable. This could create an undesirable and dangerous environment. In other instances, the lights may facilitate business transactions. If the lighting system illuminates an automobile parking lot or the interior of a business establishment, an inoperable lighting system could result in lost profits and a reduction in market share. Customer goodwill and reputation may also be damaged.
As a drawback to prior art systems, the combination of running the lamps at voltage levels near the minimum voltage level for continued operation and use of the voltage modifying devices, such as a transformer, may create unreliable operation. In some instances unwanted signal components are introduced into the power signal which disrupt operation. In the case of power reduction system configured with transformers, signal components may be introduced that disrupt desired operation. In some instances the unreliableness may be so severe as to cause the lamps to extinguish. For the above stated reasons, this is very undesirable and makes such systems unusable.
The present invention identifies the source of the problem in prior art systems and provides an inexpensive, reliable, and safe solution to the drawbacks of the prior art.
The invention described herein overcomes the drawbacks of the prior art by providing an efficient, low cost, and reliable method and apparatus to reduce power consumption. To accommodate the characteristics of certain types of loads, the method and apparatus described herein provides full power to the load for a first period of time. During this first period of time the load reaches full operating power and may thereafter be operated at a reduced power level without noticeable change in output of the load. Accordingly, during a second time period a reduced amount of power is provided to the load without an appreciable change in performance by the load. As a result the load consumes less power.
During the second period when the load is operating at a reduces power level, it is desired to provide a power signal, sufficient voltage, or sufficient current so that the load does not receive less power than is necessary to maintain desired operation. In one embodiment a signal filtering system is located to filter or clean the power signal, voltage, or current provided to the load. As a result, the conjunction with the power signal, voltage, or current that is provided to the load is of a nature sufficient to maintained operation of the load.
In one embodiment a power control system is provided that is configured to control the amount of power provided to a load. The system may comprise a timer configured to generate one or more control signals and a step-down transformer having an input node and an output node such that the output node is connected to the load. Also included is a switching system configured to selectively provide, responsive to the one or more control signals, power directly to the load or to the input of the step-down transformer. To filter or otherwise clean the signal, a capacitor connected to the output node such that unwanted signal harmonics at the output node are not provided to the load. In this embodiment the switching system provides power to the step-down transformer instead of directly to the load thereby reducing the amount of power provided to the load. The term harmonic as used herein is defined to mean any unwanted signal component. This includes unwanted signal components, such as a third harmonic, generated by a transformer.
In variations to this embodiment, the one or more control signals generated by the timer cause the switching system to provide power directly to the load during a first period and to the step-down transformer during a second period, wherein the second period is subsequent to the first period. It contemplated that the capacitor comprises a capacitor selected to provide the third harmonic to a ground node. The switching system may comprises one or more relays and the load may comprise lamps selected from the group consisting of metal halide lamps, high pressure sodium lamps, and mercury vapor lamps.
In another embodiment, the system for reducing the amount of power consumed by a lighting system comprises an input configured to connect to a source of power and a controller configured to generate one or more control signals. Also provided is a voltage control system configured to reduce the amount of voltage provided to the lighting system and a filter configured to filter unwanted signal components from the voltage provided to the lighting system. Further provided is one or more relays, responsive to the one or more control signals, configured to selectively activate the voltage control system to thereby reduce the amount of voltage provided to the lighting system such that the controller does not activate the voltage control system until after the lighting system operates at full power for a time sufficient to sustain operation at the reduced amount of voltage. In one embodiment, the voltage control system comprises a transformer. The system may further include a timer or a sensor configured to control activation of the system.
A method may be enabled for controlling the power provided to a load to reduce power consumption of the load. One embodiment includes the steps of, which may be executed in various order, closing a load relay to provide power to a load and closing a transformer relay to provide power to a step-down transformer. The step-down transformer includes a stepped down output that is connected to a step down relay, wherein the step down relay also connects to a first node. The first node serves as a connection point for the load and a capacitor and the capacitor is selected to shunt unwanted signal components to ground. Next, the method includes opening the load relay while closing the step down relay so that the step down relay selectively controls power flow from the stepped down output to the first node and wherein opening the load relay and the closing the step down relay occurs after the step-down transformer and load have reached full operating capacity. The load may comprise a plurality of lamps and the capacitor may be selected to conduct harmonics created by the step-down transformer away from the load. In one embodiment the unwanted signal components comprise signal components having frequencies at or above the third harmonic.
In another embodiment the invention comprises a method for reducing power consumption of a lighting system. The method comprises the steps of providing a signal at a first voltage to the lighting system during a start-up period and thereafter activating a voltage reduction module. The voltage reduction module creates a signal having a second voltage, wherein the second voltage is smaller than the first voltage. Next, processing the signal having a second voltage to remove unwanted frequency components of the signal having a second voltage and thereafter providing the signal having a second voltage to the load after the start-up period.
In this method the start-up period may comprise a period of time during which the lighting system operates at full power. In one embodiment the lighting system comprises lamps selected from the group consisting of metal halide lamps, high pressure sodium lamps, and mercury vapor lamps. The step of processing may comprise providing the signal to a node to which a capacitor is connected to thereby remove signal harmonics. It is contemplated that in one embodiment the signal at the first voltage may comprise a signal at a voltage selected from the group of 120, 208, 277, 240, and 480 volts.
Additional details and variations of the invention are described in more detail below. It is contemplated that the features and elements may be described in combination or alone.